1. Field of the Invention
The present invention relates to an apparatus for automatically changing bobbins, i.e., dolling a package and donning an empty bobbin, at a winding machine having a plurality of work stations disposed along the lengthwise direction of a machine frame.
In machines for winding a yarn, such as a draw texturing machine (DTY) , a draw twister (DT machine), a twisting machine, a double twister, a rewinding machine, a yarn winding machine, a film winding machine, or a glass fiber winding machine, a plurality of work stations are disposed along the lengthwise direction of a machine frame.
When a package is wound in such a winding machine, after the full wound package is doffed, an empty bobbin is donned, and the winding operation is continued.
Winding machines are roughly classified into two types. In a first type, the work station has a vertical spindle and a bobbin for winding a yarn is vertically supported by the vertical spindle. In the other type, a bobbin for winding a yarn is almost horizontally supported by a cradle.
Although the present invention is applicable to both types, it is preferably an apparatus for changing bobbins, i.e., doffing a full package and donning an empty bobbin, in a winding machine wherein a bobbin Sot winding a yarn is almost horizontally supported by a cradle.
2. Description of the Related Art
Conventional apparatus for doffing full packages and donning empty bobbins are roughly classified into two types:
(1) a so called simultaneous type doffer which is installed on a machine frame and which simultaneously doffs all full packages from the machine frame; and
(2) a so called movable type doffer wherein a truck moves along a machine frame and which sequentially doffs full packages and dons empty bobbins.
Since doffing operations are performed at all the work stations by the simultaneous doffer, small packages, which are less than the full package to be doffed, are also doffed. Further, it is very difficult to install such a simultaneous type doffer to an already installed winding machine, such as a DTY machine, which has not been prepared for the installation of doffer equipment prior to it being installed.
Contrary to this, it is said that the movable type doffer is superior to the simultaneous type doffer because of the following reasons. The movable type doffer can be introduced to an already installed winding machine. Further, the doffed full packages can be automatically stored in a peg type stand for storing packages together with a doffing operation by a movable type doffer. In addition, one movable truck is sufficient for a plurality of winding stations.
However, generally speaking, in winding machines, including draw texturing machines, although the precisions in prefabrication of each winding device are sufficiently high, the relative locational relationships between the winding devices, especially between those belonging to different work stations, are not taken into consideration. For example, if the heights from the floor on which the machine frame is installed or the distances from the working area are measured, there can be observed a large variation between the work stations.
The above-mentioned auto doffer repeats its movement and stoppage along the lengthwise direction of the machine frame and also repeats its doffing operations, which are entirely the same at all the work stations, based on the location where it stops.
As described above, a conventional winding machine per se has a large variation between its work stations, and accordingly, the locations, based on which the operations start, are not identical between the work stations. Therefore, doffing operations cannot be assured.
In order to enhance assurance of the doffing operation, when an auto doffer such as described above is intended to be used in a conventional winding machine, the floor on which the winding machine is installed is flattened first, and then base rails are disposed with high precision at the locations where the auto doffer moves. Further, the winding machine is reconstructed so that both the preciseness in the relative locational relationships between winding devices disposed along the lengthwise direction of the winding machine and the preciseness of the prefabrication of the winding devices are enhanced.
As a result, when a conventional auto doffer is intended to be used, a very large reconstruction and a lot of costs for reconstruction are required. Therefore, the conventional auto doffers have not been practically used.
Further, U.S. Pat. No. 4,615,493 proposes an improved movable type doffer, which can be referred to as a "doffing robot" by which such a large reconstruction of the floor can be neglected. However, since this doffing robot moves on base rails, it still requires a large amount of expense for installing accompanying equipments, such as base rails disposed outside the DTY machine, and accordingly, a large space for installing the accompanying equipments. Consequently, the doffing robot cannot be readily used in a plant which has not been intended to use such a doffing robot. In addition, there is a problem that setting of a doffing program for a doffing robot is somewhat complicated. Further, there is another problem that a small package, which is less than a full package due to some reason such as yarn breakage during winding operation, is doffed together with other packages because a doffing robot usually doffs all the package in a predetermined operational time.